A typical vibratory gyroscope that utilizes MEMS technology includes a proof mass that is suspended above a cavity in semiconductor substrate by a mechanical suspension system that includes flexible beams. The proof mass is driven into resonance in a drive direction by an external periodic electrostatic or electromagnetic force. When the gyroscope is subjected to an angular rotation, a sinusoidal Coriolis force is induced in a direction orthogonal to the drive-mode oscillation at the driving frequency. The Coriolis force is proportional to the amplitude of the drive motion and to precisely determine the rotation rate around the rotation axis, a feedback control system is necessary to assure a constant-amplitude oscillation of the proof mass in the drive direction. Since the output of the gyroscope is typically very small, the control system also forces the proof mass to vibrate at resonance to achieve maximum sensitivity.
Conventional gyroscopes use a self-oscillating loop architecture including several filtering stages and a phase-locked loop (PLL) to produce a clean signal with the same frequency as the drive frequency. The performance of these conventional gyroscopes, however, may be degraded due to noise and parasitic signals. Also, conventional gyroscopes can be more costly to manufacture due to the incorporation of complex filter stages.